.\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk>
.\"
.\" SPDX-License-Identifier: LGPL-2.0-or-later
.\"
.TH io_uring_prep_fadvise 3 "March 13, 2022" "liburing-2.2" "liburing Manual"
.SH NAME
io_uring_prep_fadvise \- prepare a fadvise request
.SH SYNOPSIS
.nf
.B #include <fcntl.h>
.B #include <liburing.h>
.PP
.BI "void io_uring_prep_fadvise(struct io_uring_sqe *" sqe ","
.BI "                           int " fd ","
.BI "                           __u64 " offset ","
.BI "                           __u32 " len ","
.BI "                           int " advice ");"
.BI "
.BI "void io_uring_prep_fadvise64(struct io_uring_sqe *" sqe ","
.BI "                             int " fd ","
.BI "                             __u64 " offset ","
.BI "                             off_t " len ","
.BI "                             int " advice ");"
.fi
.SH DESCRIPTION
.PP
The
.BR io_uring_prep_fadvise (3)
function prepares an fadvise request. The submission queue entry
.I sqe
is setup to use the file descriptor pointed to by
.I fd
to start an fadvise operation at
.I offset
and of
.I len
length in bytes, giving it the advise located in
.IR advice .

The
.BR io_uring_prep_fadvise64 (3)
function works like
.BR io_uring_prep_fadvise (3)
except that it takes a 64-bit length rather than just a 32-bit one. Older
kernels may not support the 64-bit length variant. If this variant is attempted
used on a kernel that doesn't support 64-bit lengths, then the request will get
errored with
.B -EINVAL
in the results field of the CQE.

This function prepares an async
.BR posix_fadvise (2)
request. See that man page for details.

.SH RETURN VALUE
None
.SH ERRORS
The CQE
.I res
field will contain the result of the operation. See the related man page for
details on possible values. Note that where synchronous system calls will return
.B -1
on failure and set
.I errno
to the actual error value, io_uring never uses
.IR errno .
Instead it returns the negated
.I errno
directly in the CQE
.I res
field.
.SH SEE ALSO
.BR io_uring_get_sqe (3),
.BR io_uring_submit (3),
.BR io_uring_register (2),
.BR posix_fadvise (2)
